There’s a Demon King Inside the Hero

Chapter 0 - Prologue



0. Prologue

“How dare you… How dare you… How daaaaare youuu!”

The evil of this world, commonly referred to as the Demon King, screamed at me.

I, Kim Suhyeon, lowered my body and adjusted my grip on the Holy Sword.

‘If you defeat the Demon King, I will let you return to your original world.’

It had been 105 years since I was summoned as a hero to this world of ‘Altera’ by a god’s words, just before I was hit by the truck that frequents reincarnation stories in my previous life.

Though all that time had passed, Suhyeon hadn’t aged and still appeared as he did when he came here—24 years old.

Suhyeon had formed bonds with adventurers, elves, dwarves, royalty, knights, and beastmen in this world, beings he had only encountered in fantasy novels.

And among them was the Demon King, the leader of the monsters, the immovable enemy of this world.

Finally, the moment had come for him to put an end to it all as the hero summoned to this world.

All the races of this world had united, struggling to drive the Demon King out and destroying the monsters that followed him, ultimately reaching his stronghold, the Demon Castle.

The soldiers of the kingdom, his comrades, and various races had joined forces to hold back the monsters pouring out of the Demon Castle, opening the path for Suhyeon to reach it.

‘May the blessings of the World Tree be with you.’

‘Show the Demon King the swordsmanship my father taught you!’

‘When this is over, let’s have a drink at the tavern, Hero!’

Leaving behind the cheers and support of everyone, Suhyeon now faced the final battle against the Demon King.

In the capital of the kingdom called Argen, where Suhyeon had first been thrown into this world, he had initially refused to become a hero, overwhelmed by the absurdity of the situation.

‘Save the world? There are strange monsters running rampant in my own world too, damn goddess!’

He had once vented his frustrations in this way, but over time, he came to understand.

That even in this world, people had lives.

They had the resolve to do anything to protect their lives, their families, and their friends from the threats of monsters.

But they lacked the power to defeat the Demon King.

That’s why they longed for a hero… someone to lead them.

Moved by their desperation, Kim Suhyeon decided to become that hero.

The Demon King was a figure that could rightfully be called a devil.

He had blood-red skin, massive horns protruding from both sides of his head, and a face resembling a skull.

His colossal, muscular body was as big as a building, with equally massive wings on his back.

Just from his appearance, it was clear.

He was the embodiment of evil in this world, the final boss.

“After killing all the monsters I summoned and my followers, now you intend to kill me as well, Hero?”

The Demon King’s arms had been severed, and his wings were torn to shreds, with blood dripping from the wounds.

Suhyeon smiled at him.

“Why, feeling bitter? You should’ve lived a righteous life.”

“Youooooo!”

The Demon King’s roar echoed, shaking the Demon Castle.

In the space behind the Demon King, dozens of enormous magic circles appeared.

Screeeeech!

Raaaawr!

The monsters poured out of the magic circles like a flood, charging at Suhyeon.

It was the 7th-class magic “Gate,” known as the limit of magic.

“Not yet!”

Following it, the 6th-class magic “Meteor” was cast.

Dozens of meteors shot out from the magic circles, crashing toward Suhyeon.

These high-level spells, which would normally exhaust any mage after a few casts, were being fired like machine gun rounds by the Demon King, even with both his arms severed.

Indeed, the Demon King was the Demon King.

As the King of Monsters, he was also highly skilled in magic.

He was the one who opened the rifts to the Demon World, summoning monsters en masse and plunging this world into fear.

But

I am a Hero as well.

Suhyeon pulled back the Holy Sword and then swung it forward with force.

In sync with his movement—

Screeeeech!

A blindingly white, sharp light burst out from the blade of the Holy Sword.

‘Sword Aura.’

By infusing one’s magic into the sword, this 6th-class magic allows for a greater range and power than a normal swing.

However, the Hero’s Sword Aura was far beyond ordinary.

The fierce light extending from the Holy Sword shattered the floor and walls of the Demon Castle, growing larger and larger.

Suhyeon slashed horizontally with the sword filled with Sword Aura.

The immense powers of both clashed in the same space.

“Demon King!”

“Hero!”

The towering light pillar that followed Suhyeon’s swing tore through the oncoming monsters and meteors, grinding them to dust.

“Arrgh!”

The Demon King’s body was also cleaved in two by the Sword Aura.

“You… you truly are…!”

With a heavy thud, the Demon King’s massive body crumbled.

“Don’t make me laugh… don’t make me laugh…”

The Demon King, now reduced to just his upper body, twisted his face toward Suhyeon.

Screeeeech…

As the air trembled, a magic circle began to form around the Demon King’s body.

“In the name of the Demon King, I curse you… This is no mere threat. As the King of Monsters and the King of Magic, I swear with all that I am… even if you flee, this curse will follow you…”

The Demon King’s head fell to the ground as he muttered his final words.

With the caster’s death, the magic he had attempted to invoke also dissipated, and the oppressive atmosphere along with the magic circle faded away.

“Haa… haa… haa…”

Now, the only sound left in the castle was Suhyeon’s heavy breathing.

“…It’s over.”

Suhyeon’s face brightened as he let out a triumphant shout, a mix of relief and joy.

“Hahaha! It’s over, it’s finally over!”

Raising the Holy Sword, Sword Aura burst forth once again.

The Sword Aura shot through the Demon Castle and reached up into the sky.

The light was visible even to those fighting monsters outside the castle.

Suhyeon had promised that if he won, he would raise the Sword Aura above the Demon Castle.

A chorus of cheers erupted from the many races fighting outside the castle.

“Wooaaaaaah!”

“We won!”

“We did it!”

Then, without warning, Suhyeon’s body began to glow.

It was the same light as when the gods delivered their decree.

‘You’ve done it!’

It was the same light and voice Suhyeon had seen and heard when he was first thrown into this world.

After spending 105 years in this world and defeating the Demon King, Suhyeon finally heard the voice of the god again.

“Are you kidding me, you damn god! There’s a limit to how irresponsible you can be!”

‘I’m sorry I couldn’t explain everything before. It took a considerable amount of magical power just to bring you to this world. Still, I adjusted your body and magic to the best possible level within the human capacity. Thanks to that, defeating the Demon King shouldn’t have been too difficult.’

“Well… that’s true. This body is incredibly light, unlike my original one.”

‘I’m glad you noticed.’

After a brief pause, the god continued.

‘So, Kim Suhyeon, are you going to return to your original world?’

“Yes.”

There was no hesitation in his answer.

“I have something I need to do when I return to my world.”

Suhyeon clenched his fist.

With the power I gained here, I can definitely do it.

Monsters had appeared in his original world as well. Though they were called “monsters” there, with this power, wiping them all out would be a piece of cake!

‘I understand. Then, I will return you to your original world right away.’

Suhyeon took a moment to listen to the cheers coming from outside the Demon King’s castle.

He had met countless people in this world, and he had led many of them.

And now, he was returning to his original world.

There was a tinge of regret—perhaps it was attachment.

But he had already decided what he needed to do once he returned to his world.

He would become a hunter, eliminating monsters and saving his world, just as he had saved this one.

“Oh man, I feel like crying…”

Unconsciously, his eyes grew misty.

Sorry… for leaving without saying goodbye.

Now, he had lived in this world longer than he had in his original one.

He had met many people here, cried with them, laughed with them, and relied on them.

No one in this world knew that he would return to his original world once he defeated the Demon King.

If he had told them, it would have made it harder to part.

Goodbye, everyone!

With a determined heart, Suhyeon entrusted himself to the light.

As he felt his body slowly being engulfed by the light, he began to drift into a haze.

Until the god spoke again.

‘Oh, by the way, the enhancements I gave to your body and magic will disappear completely once you return to your original world. Just a heads-up.’

“…?”

Wait, hold on.

“Hey! You damn son of a-!”

Pwoosh!

The light shrank instantly, disappearing along with Suhyeon. Only the Holy Sword, left without its owner, clattered as it rolled across the floor.

‘Hmm…?’

The god tilted his head.

“Could it be… the Demon King?”

Did the final spell he cast actually succeed?

Just before Suhyeon vanished, a small light, like a firefly, had emerged from the Demon King’s corpse and rushed toward him. As soon as Suhyeon disappeared, that red light vanished along with him.

‘…Regardless, he has returned to his original world. It shouldn’t affect this world. I hope he enjoys his time there…’

***

“You brat!”

Suhyeon, lying in a hospital bed, suddenly bolted upright, smelling alcohol. Bandages covered various parts of his body, and his muscles ached to the point of making him grimace.

Just before coming to this world, the god had said that the time he spent here would feel like a fleeting moment in his original world.

Judging by the situation, it seemed he had returned right after being hit by the truck and taken to the hospital, with his treatment nearly complete.

“Wow, I’m back.”

Damn god. You could’ve at least warned me. He sighed deeply and lay back down on the bed.

“…What do I do now?”

He had come back with grand ambitions of becoming a hunter and protecting people in his original world.

But without the powers he had in the other world, he was just an ordinary guy with a bunch of otherworldly knowledge—a late-blooming adolescent with delusions of grandeur.

“Haa…”

And then it happened.

[Where is this place? What is that strange smell of alcohol?]

An unexpected voice echoed in his head as he clutched his aching head.

“…What the hell?”

It was a deep, commanding voice that even seemed to carry a sense of dignity. The voice was echoing in his mind.

This voice… It sounds familiar.

…Ah!

Except for the fact that it was in his head, it sounded exactly like the voice of the Demon King he had killed.

[Hmm? Why am I hearing someone else’s voice… No?]

The voice seemed to have picked up on Suhyeon’s thoughts.

‘No way…’

[You, no way…]

The fact that the voice was responding to his thoughts without him speaking aloud meant one thing: this guy could read Suhyeon’s thoughts.

‘…Demon King?’

[…Hero?]

Whhoooosh—

The hospital curtains fluttered in the breeze.

“Shit!”

“Shit!”

 


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